Mosaic Problems . . . Can't Image Solve after a crop?

[Terry Danks]

I can use the Image Solver successfully on my integrated masters.
But after applying a very small crop to ensure cruddy edges are trimmed away, prior to mosaicing, Image Solver invariable fails?

[bulrichl]

Hi Terry,

when Image Solver script fails, it generates the following error message:

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Please check the following items:
- The initial coordinates should be inside the image.
- The initial resolution should be within a factor of 2 from the correct value.
- Adjust the star detection sensitivity parameter, so that the script can detect most of the stars in the image without mistaking noise for stars.
- The catalog should be matched to the image. Choose the appropriate catalog and magnitude filter, so that the number of stars extracted from the catalog can be similar to the number of stars detected in the image.
-------------------------------------------------

Currently (PixInsight 1.8.8-5), the crop process removes the following FITS keywords from the FITS header:
XPIXSZ, YPIXSZ, FOCALLEN, RA, OBJCTRA, DEC, OBJCTDEC, EQUINOX

The coordinates RA, DEC of the FITS header are used as seed parameters by the ImageSolver script. If these data are not present in the FITS header, the coordinates that are set manually in the ImageSolver script are used. If the manually set values are wrong, ImageSolver will fail. In addition, the manually set values for image resolution must consider any drizzle scale!


Please also see the discussion about whether it is really necessary to delete astrometric solutions when the crop process is applied: https://pixinsight.com/forum/index.php?topic=14592

Bernd

[Terry Danks]

Hi Bernd:
Many thanks for your detailed reply. It is most appreciated.

I went to bed scratching my head over this problem last night. It just made no sense. Furthermore, I have recently completed a mosaic comprised of 21 frames using IS, MBC and GMM and had no such difficulty solving after a small crop to ensure proper fit of the panels.

This AM, after reading your reply, I tried again to use Image Solver on a frame after a small crop, actually the very same cropped files from last night  . . . and had no difficulty whatsoever! So, as far as I can tell, whatever "problem" existed was "solved" by the reboot when I turned the machine on this AM. I cannot imagine what that might have been?
Anyhow, that difficulty is solved. Now I have another . . . a new topic for that one.
Thank-you, again.